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Abstract

Control over the spectral phase of a light pulse is a fundamental step toward arbitrary signal generation in a spectral band. For the terahertz spectral regime, pulse shaping holds the key for applications ranging from ultra-high speed wireless data transmission to quantum control with shaped fields. In this work, we demonstrate a technique for all-optical and reconfigurable control of the spectral phase of a light pulse in the important terahertz (THz) band. The technique is based on interaction of a guided THz pulse with patterned photoexcited regions within a uniform silicon-filled parallel-plate waveguide. We use this platform to demonstrate broadband and tunable positive and negative chirp of a THz pulse, as well as control of the pulse carrier envelope phase.

Figures (4)

Fig. 1 (a) Schematic representation of the experiment where a broadband single-cycle THz pulse is coupled in a PPWG. The dielectric-filled waveguide is pumped with a NIR pulsed source which is spatially patterned using a SLM. A CMOS camera records the intensity profile reflected by a beamsplitter. (b) Cross-section of the PPWG where a spatially shaped pump photoinduces a phase-shifting reflector for the THz pulse.

Fig. 3 Imparting broadband ±π/2 phase changes to an incident THz pulse using engineered photoconductive reflective interfaces within the waveguide. The data sets show the reflected THz signal as well as the pump intensity profile of the single line generated by the SLM and recorded by the CMOS camera. (a) −π/2 phase flip, (b) 0 phase flip, and (c) +π/2 phase flip along side the intensity profile employed.

Fig. 4 Positively chirped THz electric field (a) and associated STFT intensity (b) for a shadow-masked sample pumped with 100 μJ pump energy. Negatively chirped THz electric field (c) and associated STFT intensity (d). The pump-intensity profile generated using the SLM and captured by the CMOS array is shown in the insets (b and d). The cyan solid lines (b and d) shows the position of the intensity maxima and the black dashed curve the maxima position predicted from the mask design (b) or pump intensity profile (d).